An Internet Protocol-Digital Subscriber Line Access Multiplexer (IP-DSLAM) shelf typically includes one or two Line Termination cards and a single Network Termination card placed into respective slots on the shelf. Each Line Termination card includes a number of ports, each port serving a user. Each Line Termination card connects to the Network Termination card, which in turn establishes communications between the Line Termination cards and the aggregation network.
An example IP-DSLAM is the 7330™, part of the Intelligent Services Access Manager (ISAM™) family of products by Alcatel-Lucent. This IP-DSLAM has four slots for Line Termination (LT) cards and a Network Termination (NT) card. The Network Termination card includes a 24-port GE switch. The GE switch is connected to each of four Line Termination cards through four of the ports of the GE switch, one port per Line Termination card. Four ports connect the GE switch to an IP network through the faceplate of the NT card. The remaining sixteen ports of the GE switch connect to a GE Expander Unit, through which each of the sixteen ports connects to the network, to a remote unit, or, often, to nothing and the port is not used. Each Line Termination card has 48 ports and can therefore support up to 48 users. The entire IP-DSLAM shelf can therefore support up to 192 users.
As new services are implemented within communication networks, such as video-on-demand (VOD), there is a temptation to implement the service on the ISAM rather than in the network, so as to reduce the communications and associated provisioning between the IP-DSLAM and the network. For example, in the case of VOD, content could be stored on the IP-DSLAM rather than on a server within the IP network. One solution would be to build the functionality of the new service into the Network Termination card. However, this is not very customizable and would require a new Network Termination card to be designed or built every time a new service was introduced.
A more flexible solution is to build the function into one of the slots normally used for one of the Line Termination cards by using a specialized service card. This would allow a new service to be easily added to the IP-DSLAM without changing the Network Termination card, which is typically the most complex and expensive component on an IP-DSLAM. However, using one of the slots normally used for a Line Termination card obviously reduces the number of possible Line Termination cards and hence the number of users which can be supported by the IP-DSLAM. Although the new service could be added relatively easily, the per-user cost of the IP-DSLAM would increase. In addition, the bandwidth available between a port normally supporting a Line Termination card and the GE switch is limited to 1 Gb/s, which may be insufficient for some services.
A flexible solution for adding a service to an IP-DLSAM without using one of the slots normally used for a Line Termination card would allow services to be easily added without the need to replace the Network Termination card each time a service was added or changed, and would not reduce the number of users which can be supported by the IP-DSLAM.